A thin AlGaN layer, which is suitable for structural study using Rutherford backscattering (RBS)/channeling, was grown on an Al2O3(0001) substrate by metalorganic chemical vapor deposition. The results show that the composition of the epilayer is Al0.05Ga0.95N and that although the epilayer is very thin (79 nm), it has a good crystalline quality (chi (min) = 1.9%). The azimuthal orientation of the AlGaN epilayer relative to the Al2O3 substrate is AlGaN[0001] // Al2O3[0001] and AlGaN{1120} // Al2O3{1010}, showing that the AlGaN epilayer is rotated by 30 degrees around the [0001] axis with respect to the Al2O3 substrate which decreases the lattice mismatch between the epilayer and the substrate significantly. RES angular scan was used to determine the strain-induced tetragonal distortion of the epilayer. Combined with X-ray diffraction, the perpendicular and parallel elastic strains of the AlGaN layer, e(perpendicular to) = +0.31% and e(parallel to) = -0.28%, can be calculated. (C) 2001 Elsevier Science B.V. All rights reserved.